One of the problems in the pharmaceutical industry resides in the provision of safety caps for containers for poisons or other dangerous materials, particularly with regard to children too young to understand the poison symbol or to read warnings. Many suggestions have been made in this connection but most of the prior art constructions are too expensive and complicated for every day use, and it is the particular object of the present invention to provide a safety closure cap which cannot be removed by children wherein said closure cap is a simple one-piece plastic part.
There is the well known palm and turn cap which in most cases is difficult even for an adult to operate. There is also the overcap type which is expensive because it uses two cap parts.
The present invention is directed to the type of safety cap wherein a substantially self-sustaining but deformable upwardly extending dome is adapted to be pressed downwardly centrally thereof to release interengaging means at the edge of the container so that the cap may be removed, and in order to replace, it merely has to be snapped on.
One example of this type of cap is U.S. Pat. No. 3,484,016, which however is not a safety cap because of the fact that it releases with only one motion and is therefore not safe, whereas in safety caps, two motions are necessary. In the patent identified, when pressure is applied as described therein, the surrounding continuous skirt at 16 moves generally upwardly on fulcrum 18a for instance, thus merely be pressing down on the dome the entire cap is immediately released.
Referring to column 3, lines 38 et seq of this patent, it is described that there may be a possibility that the cover member (periphery of the cap) may not quite clear the curved surface around the outside of the mouth portion of the container, and if this happens the cover member may be removed by the application of lateral pressure as indicated by the arrow 26a in FIG. 5, but this is not expected to occur. The principal object of the invention in the patent is to release the cap by a single motion as shown by arrow 19 in FIG. 2. In any event it will be clear in FIG. 5 that the skirt 16 rises and rises either above the surrounding curved surface 13 or opposite it, so that the cover is actually fully released. Also in the patent the same is rather difficult to operate because of the fact that the skirt 16 is continuous and it has to stretch in order to move from the FIG. 1 condition thereof into the FIG. 2 condition thereof. It can stretch to some extent because it is made of rubber, but when made of flexible plastic material such as polyethelene it often fails to operate and is broken under excessive pressure used at 19 in FIG. 2 to try to operate it. If pressure is released from the dome the cover will come off without further effort, at least that is what it is expected to do.
All of these objections are avoided by the present invention in which the cover is not completely dislocated from the container by the application of pressure downwardly on the dome thereof. If the pressure is released the cap periphery moves back into locking engagement with respect to the container so it will be seen that in the present invention a true safety device is presented which definitely requires two motions and usually two hands in order to operate it. In addition in the present case, slits are utilized in the surrounding skirt and this makes the operation easier although it does not in any case cause the cover to be released by a single motion as in the patent identified.